Bus bar for battery packs

ABSTRACT

A battery pack has bus bars at one end, freeing the other end of the battery pack for cooling or other arrangements. A plurality of battery cells has first terminals of the battery cells at first ends of the battery cells. Portions of second terminals of the battery cells are at the first ends of the battery cells. The first ends of the battery cells are in a coplanar arrangement. A plurality of bus bars is assembled proximate to the first ends of the battery cells. The bus bars are coupled to the first terminals and the second terminals of the battery cells at the first ends of the battery cells to place the battery cells in one of a series connection, a parallel connection or a series and parallel connection.

BACKGROUND

A bus bar is a metal strip or bar that conducts electricity and is usedfor electrical power distribution. Battery cells can be connected withbus bars to make battery packs. Some battery packs using cylindricalcells make electrical connections to the tops and the bottoms of thecells. When connecting cells in series, bus bars and high currentinterconnects link the positive terminal of one cell, or a parallelgroup of cells, to the negative terminal of the next cell or the nextparallel group of cells. However, connections to the bottoms of thecells obstruct airflow or liquid flow from cooling mechanisms utilizedto remove heat generated by the cells. In addition, the high currentinterconnect from the bottoms of the cells to the bus bars, which may bein the form of a wire somewhat longer than the length of a cell,introduces a small amount of resistance which gives rise to a voltagedrop at high current levels. Assembly of this wire to the bus bars or tothe bottom of the battery adds costs to a battery pack and may introducereliability issues.

It is within this context that the embodiments arise.

SUMMARY

One embodiment of a battery pack has a plurality of battery cells and aplurality of bus bars. The battery cells have first terminals of thebattery cells at first ends of the battery cells. The battery cells haveportions of second terminals of the battery cells at the first ends ofthe battery cells. The first ends of the battery cells are in a coplanararrangement. The plurality of bus bars is disposed proximate to thefirst ends of the battery cells. The plurality of bus bars is coupled tothe first terminals and the portions of the second terminals of thebattery cells at the first ends of the battery cells to place thebattery cells in one of a series connection, a parallel connection or aseries and parallel connection.

Another embodiment of a battery pack has a cell holder, a plurality ofbus bars and a plurality of battery cells. The plurality of bus bars ispositioned at a first end of the cell holder. The plurality of batterycells is arranged in the cell holder. Each of the battery cells has afirst terminal proximate to the plurality of bus bars. Each of thebattery cells has a portion of a second terminal proximate to theplurality of bus bars. The first terminal and the portion of the secondterminal are electrically coupled to the plurality of bus bars at afirst end of the battery cell. The battery cells are in one of aparallel connection, a series connection, or a parallel and seriesconnection.

A method of assembling a battery pack is provided. The method includesarranging a plurality of battery cells so that first ends of the batterycells are coplanar. Each of the battery cells has a first terminal of afirst polarity at the first end of the battery cell and a portion of asecond terminal of a second polarity at the first end of the batterycell. The method includes arranging a plurality of bus bars proximate tothe coplanar first ends of the battery cells. Coupling the plurality ofbus bars to the first terminals and the second terminals of the batterycells is included in the method. The coupling is at the first ends ofthe battery cells thereby leaving the opposing end available for heatremoval. The battery cells may be coupled in one of a series connection,a parallel connection, or a series and parallel connection.

Other aspects and advantages of the embodiments will become apparentfrom the following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the described embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings. These drawings in no waylimit any changes in form and detail that may be made to the describedembodiments by one skilled in the art without departing from the spiritand scope of the described embodiments.

FIG. 1 is a schematic diagram of a battery pack with bus bars above andbelow the battery cells.

FIG. 2A is a schematic diagram of a battery pack with bus bars adjacentto the positive terminals of the battery cells, in accordance with oneembodiment.

FIG. 2B is a cross-section view of bus bars in a layer stack, in anembodiment of the battery pack of FIG. 2A.

FIG. 3 is a perspective view of a cell holder in accordance with oneembodiment.

FIG. 4 is a perspective view of a battery pack with a bus bar layer atone end of the battery pack, in accordance with one embodiment.

FIG. 5 is a perspective view of the battery pack of FIG. 4 with aninsulator layer on top of the bus bar layer.

FIG. 6 is a perspective view of the battery pack of FIG. 5 with anotherbus bar layer on top of the insulator layer.

FIG. 7 illustrates bus bars with interleaved fingers in accordance withone embodiment.

FIG. 8 is a perspective view of bond wires coupling a bus bar to aterminal of a battery cell at one end of the battery cell in accordancewith one embodiment.

FIG. 9 is a flow diagram of a method for making a battery pack havingthe bus bars at a single end of the battery cells in accordance with oneembodiment.

DETAILED DESCRIPTION

Detailed illustrative embodiments of a battery pack where the bus barsare located proximate to one end of the battery terminals to leave theopposing end accessible to a heat sink are provided herein. However,specific functional details disclosed herein are merely representativefor purposes of describing embodiments. Embodiments may, however, beembodied in many alternate forms and should not be construed as limitedto only the embodiments set forth herein.

It should be understood that although the terms first, second, etc. maybe used herein to describe various steps or calculations, these steps orcalculations should not be limited by these terms. These terms are onlyused to distinguish one step or calculation from another. For example, afirst calculation could be termed a second calculation, and, similarly,a second step could be termed a first step, without departing from thescope of this disclosure. As used herein, the term “and/or” and the “I”symbol includes any and all combinations of one or more of theassociated listed items.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising”, “includes”, and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. Therefore, the terminology usedherein is for the purpose of describing particular embodiments only andis not intended to be limiting.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

One type of battery pack, as shown in schematic form in FIG. 1, uses busbars above and below the battery cells to connect the battery cells in aparallel, series or series-parallel manner, which limits the ability toremove heat generated by the cells of the battery pack. By contrast,embodiments of the battery pack of FIGS. 2A and 4-7 have bus bars onlyat one end of the battery cells or the cell holder, in variousarrangements as will be further discussed below. The battery packsdescribed herein may be used with lithium-ion battery cells or othertypes of rechargeable battery cells, and may be used in electricvehicles, hybrid vehicles and other applications. Electric vehicles andhybrid vehicles include land based motor vehicles as well as air basedvehicles, such as airplanes, helicopters, rockets, spaceships, etc., andwater based vehicles, such as boats, submarines, etc. It should beappreciated that the embodiments may also be integrated withnon-rechargeable battery cells.

FIG. 1 shows a battery pack 100 with a first group of battery cells 102,104 in a parallel connection, a second group of battery cells 106, 108in a parallel connection, and a third group of battery cells 110, 112 ina parallel connection. The first group, the second group and the thirdgroup are coupled in a series connection. Bus bars 114, 116, 118, 120,122, 124 are used to connect the battery cells in this parallel andseries coupling. Each of the bus bars is coupled to the respectivebattery cells with one or more wires. A relatively thick wire couplesthe second bus bar 114 to the third bus bar 122, making a seriesconnection for the first group and the second group of battery cells.Another relatively thick wire couples the fourth bus bar 116 to thefifth bus bar 124, making a series connection for the second group andthe third group of battery cells, so that the sixth bus bar is thepositive terminal for the battery pack 100.

FIG. 2A shows a battery pack 200 with a bus bar arrangement enablingefficient heat removal from one end of the battery pack as all the busbars are proximate to the other end of the battery pack. In thisembodiment, the bus bars 214, 216, 222, 218 are assembled proximate toone end of the battery cells, enabling the use of fewer bus bars than inthe battery pack of FIG. 1. The relatively thick wires from upper busbars to lower bus bars are eliminated in the embodiment of FIG. 2A. Thebattery pack 200 makes use of the access to both positive and negativeterminals at one end of the cells, e.g., a top end of the cells, bycoupling the bus bars to the positive and negative terminals throughwires proximate to the top end of the cells. It should be appreciatedthat the embodiment of FIG. 2A enables the use of wires that are shorterin length than any of the battery cells. As shown in FIG. 2A, the firstgroup of battery cells 102, 104 is in a parallel connection, the secondgroup of battery cells 106, 108 is in a parallel connection, and thethird group of battery cells 110, 112 is in a parallel connection. Thefirst group, the second group and the third group are in a seriesconnection with each other. Bus bars 214, 216, 218, 222 are used tocouple the battery cells in this parallel and series coupling, asfollows. Starting with the negative terminal of the battery pack 200, afirst bus bar 214 is connected to the negative terminals of the firstgroup of battery cells 102, 104 at a top end 138 of each of the batterycells. The second bus bar 222 is connected to the positive terminals ofthe first group of battery cells 102, 104 at the top end 138 of each ofthe battery cells. The first and second bus bars 214, 222 couple thefirst group of battery cells 102, 104 in parallel. The second bus bar222 and the third bus bar 216 couple the second group of battery cells106, 108 in parallel. The third bus bar 216 and the fourth bus bar 218couple the third group of battery cells 110, 112 in parallel. Seriesconnections are formed by the bus bars. The second bus bar 222 connectsthe positive terminals of the first group of battery cells 102, 104 tothe negative terminals of the second group of battery cells 106, 108.The third bus bar 216 connects the positive terminals of the secondgroup of battery cells 106, 108 to the negative terminals of the thirdgroup of battery cells 110, 112. The fourth bus bar 218 is the positiveterminal of the battery pack 200. Other arrangements of bus bars andparallel connections, serial connections, or parallel and seriesconnections are readily devised as variations. Battery cells of otherpolarities may be used in these variations. It should be appreciate thatthe connections between the battery cells and the bus bars may be madethrough wires extending through apertures defined through the layerstack as described below with reference to FIG. 2B.

The bus bars can be arranged in a layer stack 250, or in otherarrangements as will be later discussed. In the layer stack 250, thefirst bus bar 214 and the third bus bar 216 are placed in a first layer230, and are separated by a gap so as not to short-circuit. The gap maybe filled with an insulator in some embodiments, however this isoptional. An insulator is disposed as the second layer 232. The secondbus bar 222 and the fourth bus bar 218 are placed in a third layer 234,and are separated by a gap or insulator so as not to short-circuit. Thethird layer 234 is separated from the first layer 230 by the secondlayer 232, namely the insulator, so that the bus bars on differinglayers do not short-circuit. It should be appreciated that alternateconfigurations of the layer stack are possible as FIG. 2A is one exampleand not meant to be limiting. For example, the layer stack may have morethan three layers and each bus bar layer may have a single bus bar ortwo or more bus bars disposed within a single co-planar layer.

Battery cells 102-112 have a projecting nub as a positive terminal atthe top end of the cell. Battery cells 102-112 have a can or casing as anegative terminal of the cell. The casing has a relatively flat surfaceat the bottom end of the cell, cylindrical sides, and a portion of thenegative terminal at the top end of the cell. In some types of batterycells, the casing has a crimp at the top end of the cell, which isformed as the casing is sealed around the contents of the battery cell.This crimp or other portion of the negative terminal at the top end ofthe cell provides physical and electrical access at the top end to thenegative terminal of the battery cell. The crimp is spaced apart fromthe peripheral sides of the projecting nub through a gap that may or maynot be filled with an insulator.

It should be appreciated that having bus bars at both ends, i.e., thetop and the bottom, of the battery cells does not leave an area where aheat sink can be affixed to be in thermal communication with the top orbottom surfaces of the battery cells for efficient heat removal. Inaddition soldering or otherwise connecting the relatively thick wirefrom an upper bus bar to a lower bus bar involves an assembly operationwhich adds to costs of the production of battery packs. This relativelythick wire is longer than the length of any one of the battery cells andcan introduce parasitic resistance into the current path, which in turncan introduce a voltage drop under high current drain conditions. Therelatively thick wire can also be subject to breakage and contact to oneor more of the cells and attendant short-circuit, open circuit or otherreliability problems.

In one embodiment, the layer stack is formed using layers of a circuitboard. For example, the bus bars can be made of (or on) copper layers oranother suitable conductive metal and the insulator can be made of resinimpregnated fiberglass or other suitable insulator materials. Invariations, the bus bars can be made of aluminum or other metals, andvarious materials may be applied as an insulator. In one embodiment, aheat sink 252 is assembled to the bottom ends 140 of the battery cells102, 104, 106, 108, 110, 112 and is thermally coupled to the bottom ends140. The heat sink may have finning or passages for air or liquidcooling. A fan may supply air flow across a surface of the heat sink 252in some embodiments. In a variation, the heat sink is attached oraffixed to the bottom of a battery cell holder, such as the battery cellholder of FIG. 3. The co-planar arrangement of the battery cellsprovides a relatively flat surface to attach a heat sink and in someembodiments the battery cells are designed to cool efficiently throughthe bottom of the cells, e.g., 18650 Lithium ion batteries.

One way of routing wires connecting the bus bars to the battery cellterminals is shown in FIG. 2B. These wires, as shown in FIGS. 2A and 2B,can be shorter than the length of a battery cell, and are thus shorterthan and less resistive than wires connecting from overhead bus bars tothe bottoms of the battery cells as shown in FIG. 1. In FIG. 2B, each ofthe materials in the layer stack has an aperture, and the sizes of theapertures are arranged so that a bond wire 236 or other wire is lesslikely to short out to one of the bus bars. In the example shown, a busbar on the first layer 230 of the layer stack has an aperture 238,through which the bond wire 236 can pass. An insulator on the secondlayer 232 of the layer stack has a smaller aperture 240, through whichthe bond wire 236 can pass. A bus bar on the third layer 234 of thelayer stack has a larger aperture 242, through which the bond wire 236can pass. The smaller aperture 240 of the insulator, i.e., the secondlayer 232, constrains motion of the bond wire 236 so that the bond wire236 is less likely to contact edges of the larger aperture 242 oraperture 238. In other words, the bond wire 236 is less likely tocontact the bus bar on the third layer 234 or the first layer as aresult of the staggered sizes of the apertures. Bond wire 236 couplesthe bus bar on the first layer 230 to a surface 134 of a battery cell,e.g., a positive nub terminal or a negative terminal at the top of thebattery cell. The apertures of the lower bus bar, closer to the firstends of the battery cells, are larger than the apertures of theinsulator. In some embodiments the apertures are circular and thediameter of aperture 240 is less than the diameter of the aperturesthrough the bus bars above and below the insulator layer. In addition,it should be appreciated that the apertures of one layer are alignedwith apertures of another layer so that access is provided through thelayer stack. It should be further appreciated that the apertures may beany geometric configuration and are not limited to circular shapes.Other arrangements of apertures are readily devised, for example toaccommodate wires bonded or attached to another surface of a bus bar orattached in another manner. The embodiments of the stacked bus bars maybe encased within a housing for use in a particular application, such asa hybrid or electric vehicle.

FIG. 3 shows a battery cell holder 300. In the embodiment shown, thebattery cell holder 300 is made of a plastic material. Variations of thebattery cell holder 300 may be made of other materials, and may bemolded, cast or even produced using a 3-D printer. Battery cells 308 areinserted into a housing 302, and a lid 304 is attached to the housing302, for example by one or more fasteners 306 or other means. Thebattery cell holder 300 retains the battery cells in a close-pack ordense-pack, staggered row or hexagonal arrangement. Other arrangementsare readily devised as the embodiments are not limited to the hexagonalarrangement. As shown, the battery cell holder 300 is only partiallypopulated, and can readily be filled with battery cells. These can becommercially available battery cells, such as lithium ion cells or cellsof another chargeable or non-chargeable technology. In otherembodiments, the battery cells may be proprietary battery cells madeespecially for a specific battery pack. The battery cell holder 300 isshown without the bus bars, which are readily added as shown in FIGS.4-6.

FIG. 4 shows a battery pack 400, such as the battery cell holder FIG. 3or a variation thereof fully populated with battery cells. At one end ofthe housing 402, for example the top end of the housing 402, a bus barlayer is added. The bus bar layer has a first bus bar 404 and a secondbus bar 406. The first bus bar 404 couples a first group of batterycells to a second group of battery cells in series, and the second busbar 406 connects a third group of battery cells to a fourth group ofbattery cells in series. A gap separates the first bus bar 404 and thesecond bus bar 406 (similarly to the arrangement shown in FIG. 2A) sothat these bus bars do not short. The first bus bar 404 and the secondbus bar 406 extend over an entirety of the top surface of the housing402 in this embodiment. The first bus bar 404 and the second bus bar 406have apertures through which bond wires or other wires can pass to formelectrical connections with the battery cells and corresponding bus bar.

FIG. 5 shows the battery pack 400, with an insulator layer 502 added ontop of the bus bar layer. The insulator layer 502 covers the top surfaceof first bus bar 404 and the second bus bar 406 of FIG. 4, and may haveapertures through which bond wires or other wires can pass to formelectrical connections with the battery cells. As illustrated, theapertures of the insulator layer 502 are aligned with correspondingapertures of the bus bar layer of FIG. 4. FIG. 6 shows the battery pack400, with a bus bar layer on top of the insulator layer 502 of FIG. 5.In FIG. 6, the added bus bar layer includes a third bus bar 602, afourth bus bar 604, and a fifth bus bar 606. The third bus bar 602connects the first group of battery cells to another block or group ofbattery cells, e.g., in a neighboring battery pack. The fourth bus bar604 connects the second group of battery cells to the third group ofbattery cells. The fifth bus bar 606 connects the fourth group ofbattery cells to another block or group of battery cells, e.g., in asecond neighboring battery pack. Bus bars 602-604 include aperturesdefined through the surface and these apertures are aligned with theapertures of the insulator layer of FIG. 5 and the apertures of thefirst bus bar layer of FIG. 6. Thus with the corresponding apertures ofeach layer substantially aligned, access is provided for wires or leadsfrom the battery cells to each bus bar layer as illustrated withreference to FIG. 2B.

Referring to FIGS. 4-6, the first group of battery cells is thusconnected in parallel by the first bus bar 404 and the third bus bar602. The second group of battery cells is connected in parallel by thefirst bus bar 404 and the fourth bus bar 604. The third group of batterycells is connected in parallel by the fourth bus bar 604 and the secondbus bar 406. The fourth group of battery cells is connected in parallelby the fifth bus bar 606 and the second bus bar 406. Other groupings ofparallel and series connections can be formed by other arrangements andconnections of bus bars as readily devised in variations. In addition,more stacks of bus bars and insulator layer may be integrated into theembodiments discussed herein.

FIG. 7 shows an alternative technique for arranging bus bars at a singleend of a battery pack, i.e., at one end of each of the battery cells.Two bus bars 702, 704 are in coplanar arrangement, and have interleavedfingers 706, 710, in an interleaved bus bar arrangement 700. That is,the fingers 706 of a first bus bar 702 are interleaved and co-planarwith the fingers 710 of a second bus bar 704. The fingers 706 of thefirst bus bar are coupled to the negative terminals 708 of a first group720 of the battery cells. The fingers 710 of the second bus bar 704 arecoupled to the positive terminals 712 of the first group 720 of thebattery cells. In this example, the coupling from the bus bars to thepositive and negative terminals of the battery cells is via bond wiresattached at the top ends of the battery cells. The first bus bar 702 andthe second bus bar 704 connect the first group 720 of the battery cellsin parallel. Additional fingers of the second bus bar 704 are connectedto the negative terminals of a second group 722 of battery cells.Fingers of a third bus bar 724 are connected to the positive terminalsof the second group 722 of battery cells. The second bus bar 704 and thethird bus bar 724 connect the second group 722 of the battery cells inparallel. Thus, the second bus bar 704 connects the first group 720 andthe second group 722 of battery cells in series. Additional groups ofbattery cells can be connected in series by additional bus bars withinterleaved fingers, in related arrangements.

FIG. 8 shows bond wires 810 coupling or electrically connecting a busbar 808 to the negative terminal 806 of a battery cell 802, in a bus tocell wiring arrangement 800. The battery cell 802 has a nub 804 as apositive terminal, which will be later connected to another one of thebus bars. The bond wires 810 are, in one example, ultrasonically weldedto the bus bar 808 at a proximate end of the bond wire, andultrasonically welded to the negative terminal 806 of the battery cellat distal end of the bond wire. The bond wires may be aluminum, copper,silver or other conductive metals or combinations thereof. Other typesof electrical connections between bus bars and battery terminals may bedevised, such as spot welding, soldering, spring contacts, etc. Itshould be appreciated that the positive and negative electricalconnections can be made utilizing the same machine or tool in theseembodiments to further enhance manufacturing efficiencies.

FIG. 9 shows a flow diagram of a method 900 for assembling a batterypack. Variations of the method 900 are readily devised, using feweroperations, additional operations, changing the order of the operationsand so on. In an operation 902, battery cells are inserted into a cellholder or some suitable support structure for the battery cells. Forexample, the cell holder 300 and battery cells shown in FIG. 3 may beused. The battery cells are arranged with the first ends coplanar, in anoperation 904. Bus bars are arranged proximate to the first ends of thebattery cells, in operation 906. The bus bars are arranged over one endof the battery cells in a stacked arrangement in order for efficientheat removal from the opposing end. In operation 908, in one embodiment,a first bus bar and a second bus bar are placed on a first layer of alayer stack. An insulator is placed as the second layer over the firstlayer of the layer stack, in an operation 910. A third bus bar is placedon a third layer of the layer stack, in an operation 912. For example,the layer stack shown in FIGS. 2A and 2B may be used with apertures asshown in FIG. 2B. Thus, all the bus bars are assembled along a singleplane along the top of the cells to free up the area at the bottom ofthe cells for thermal management. In addition, both the positive andnegative electrical connection discussed below can be made from a singleend of the assembly thereby enabling completion of the high currentconnections without having to reposition the

In one embodiment, bond wires are passed through apertures of the layerstack, in an operation 916. The bus bars are coupled to the firstterminals and the second terminals of the battery cells, at first endsof the battery cells, in an operation 918. For example, in operation920, the first bus bar is coupled to the second terminals of a firstgroup of battery cells. In operation 922, the third bus bar is coupledto the first terminals of the first group of battery cells. In operation924, the third bus bar is coupled to the second terminals of a secondgroup of battery cells. The second bus bar is coupled to the firstterminals of the second group of battery cells, in an operation 926. Theoperations 920, 922, 924, 926 of coupling the first, second and thirdbus bars to the terminals of the first and second groups of batterycells results in a parallel-connected first group of battery cells and aparallel-connected second group of battery cells, with the first andsecond groups in series connection. Other arrangements of battery cellsare provided by variations of the method 900. In an operation 928, inone embodiment, a heat sink is attached to the bottom of the cellholder. The heat sink may have air flow or liquid flow directed over asurface of the heat sink by a further cooling mechanism, e.g., a fan ora liquid pump. Duct work or plumbing for the airflow or the liquid flow,mounting of a fan or a liquid pump, and electrical wiring for the fan orthe liquid pump are readily devised.

With the above embodiments in mind, it should be understood that theembodiments might employ various computer-implemented operationsinvolving data stored in computer systems. These operations are thoserequiring physical manipulation of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. Further, the manipulationsperformed are often referred to in terms, such as producing,identifying, determining, or comparing. Any of the operations describedherein that form part of the embodiments are useful machine operations.The embodiments also relate to a device or an apparatus for performingthese operations. The apparatus can be specially constructed for therequired purpose, or the apparatus can be a general-purpose computerselectively activated or configured by a computer program stored in thecomputer. In particular, various general-purpose machines can be usedwith computer programs written in accordance with the teachings herein,or it may be more convenient to construct a more specialized apparatusto perform the required operations.

Although the method operations were described in a specific order, itshould be understood that other operations may be performed in betweendescribed operations, described operations may be adjusted so that theyoccur at slightly different times or the described operations may bedistributed in a system which allows the occurrence of the processingoperations at various intervals associated with the processing.

The foregoing description, for the purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the embodiments and its practical applications, to therebyenable others skilled in the art to best utilize the embodiments andvarious modifications as may be suited to the particular usecontemplated. Accordingly, the present embodiments are to be consideredas illustrative and not restrictive, and the invention is not to belimited to the details given herein, but may be modified within thescope and equivalents of the appended claims.

What is claimed is:
 1. A battery pack comprising: a plurality of battery cells having first terminals of the battery cells at first ends of the plurality of battery cells and portions of second terminals of the battery cells at the first ends of the plurality of battery cells, with the first ends of the plurality of battery cells being in a coplanar arrangement; a plurality of bus bars disposed proximate to the first ends of the plurality of battery cells and coupled to the first terminals and the portions of the second terminals of the plurality of battery cells to place the plurality of battery cells in one of a series connection, a parallel connection, or a series and parallel connection, wherein the plurality of bus bars is arranged as co-planar interleaved fingers such that the fingers are coplanar, and wherein a first one of the plurality of bus bars, having first fingers, is a first component and a second one of the plurality of bus bars, having second fingers, is a second component, the first and second components arranged to be at differing electrical potentials; and a first plurality of bond wires connecting the first fingers of the first one of the plurality of bus bars to the first terminals of a first subset of the plurality of battery cells; a second plurality of bond wires connecting the second fingers of the second one of the plurality of bus bars to the portions of the second terminals of the first subset of the plurality of battery cells; and a third plurality of bond wires connecting the second fingers of the second one of the plurality of bus bars to the first terminals of a second subset of the plurality of battery cells.
 2. The battery pack of claim 1, wherein each of the plurality of battery cells comprises: a positive terminal as a first terminal; and a cylindrical can as a second terminal.
 3. The battery pack of claim 1, wherein the plurality of bus bars comprises: stacked parallel plates separated by insulator material.
 4. The battery pack of claim 3, wherein multiple bus bars are disposed on one layer of the stacked parallel plates.
 5. The battery pack of claim 1, further comprising: a heat sink coupled to second ends of the plurality of battery cells, the second ends opposing the first ends and the second ends having a co-planar arrangement, and wherein the plurality of battery cells are rechargeable battery cells.
 6. The battery pack of claim 1, wherein the plurality of bus bars includes first fingers connected to the first terminals of the first subset of the plurality of battery cells by the first plurality of bond wires and second fingers connected to the second terminals of the first subset of the plurality of battery cells by the second plurality of bond wires.
 7. The battery pack of claim 1, wherein the plurality of bus bars includes a first bus bar, an insulator and a second bus bar, in stacked parallel arrangement.
 8. A battery pack comprising: a plurality of bus bars; a plurality of battery cells, with first terminals of the battery cells coplanar and coupled to the plurality of bus bars, and second terminals of the battery cells each having a portion proximate to and coupled to the plurality of bus bars such that the bus bars couple the plurality of battery cells in one of a parallel connection, a series connection, or a parallel and series connection; and wherein a first plurality of bond wires connects a first one of the plurality of bus bars to the first terminals of a first group of battery cells; wherein a second plurality of bond wires connects a second one of the plurality of bus bars to the portions of the second terminals of the first group of battery cells; and wherein a third plurality of bond wires connects the second one of the plurality of bus bars to the first terminals of a second group of battery cells; and wherein the plurality of bus bars includes a first bus bar having first fingers coupled by the first plurality of bond wires to the first terminals of the first group of battery cells and a second bus bar having second fingers coupled by the second plurality of bond wires to the portions of the second terminals of the first group of battery cells, wherein the first bus bar with first fingers is a first component and the second bus bar with second fingers is a second component arranged to be at a differing electrical potential from the first component, wherein the first fingers are interleaved with the second fingers, and wherein the first fingers and second fingers are coplanar.
 9. The battery pack of claim 8, wherein the first terminals are at first ends of the battery cells, and wherein second ends of the battery cells are coplanar.
 10. The battery pack of claim 8, further comprising a heat sink coupled in a thermal manner to second ends of the battery cells, wherein first ends of the battery cells include the first terminals of the battery cells.
 11. The battery pack of claim 8, wherein the plurality of bus bars has a plurality of apertures therethrough dimensioned for passage of wires, and further comprising: the second plurality of bond wires passing through one or more apertures of both the first one of the plurality of bus bars and the second one of the plurality of bus bars to connect the second one of the plurality of bus bars to the portions of the second terminals of the first group of battery cells.
 12. The battery pack of claim 8, wherein the plurality of battery cells includes the first group of battery cells connected in parallel, the second group of battery cells connected in parallel, and the first group of battery cells connected in series with the second group of battery cells via the second one of the plurality of bus bars and the second and third pluralities of bond wires. 